Abstract

We present a general purpose algorithm for finding low-weight codewords as well as for decoding a received codeword in any quasi-cyclic code whose length and dimension is a multiple of a power of 2. In this paper, we apply the algorithm on a McEliece variant recently proposed by Misoczki et al. (MDPC-McEliece: New McEliece variants from moderate density parity-check codes, 2013). In their paper, the authors present instances of LDPC codes with increased weight for use in a McEliece type PKC. They claim that all message-recovery and key-recovery attacks can be avoided. We show that this is not true for certain parameters and public-key matrices.